An apparatus has heretofore been developed and proposed to successively make plastic bags each of which includes a bottom gusset portion incorporated into superposed two layers of panel portion, as disclosed in Japanese Laid-Open Patent Publication No. 254,984 of 2,000. The plastic bag may include side gusset portions.
In the apparatus of the publication, webs of panel material are superposed into two layers and fed longitudinally thereof. In addition, sheets of side gusset material are folded into halves and supplied to and put on one of the layers of panel material one by one before the layers of panel material are superposed with each other, to extend widthwise of one of the layers of panel material. Furthermore, a web of bottom gusset material is supplied to and put on one of the layers of panel material and folded into halves. The web of bottom gusset material extends longitudinally of one of the layers of panel material to be disposed along one of the side edges thereof. The layers of panel material are then superposed with each other so that the sheets of side gusset material and the web of bottom gusset material can be interposed between the layers of panel material. The web of bottom gusset material may be supplied to the webs of panel material after the layers of panel material are superposed with each other. The layers of panel material are then heat sealed with the web of bottom gusset material by longitudinal seal means. In addition, the layers of panel material are heat sealed with the sheets of side gusset material by cross seal means. The webs of panel material are then cut widthwise thereof by a cutter at the position of the sheet of side gusset material. The apparatus can therefore successively make plastic bags each of which includes a bottom gusset portion formed by the web of bottom gusset material and incorporated into superposed two layers of panel portion which are formed by the webs of panel material. The plastic bag further includes side gusset portions formed by the sheets of side gusset material.
However, in this case, the apparatus involves not only side gusset material supply means by which the sheets of side gusset material are supplied but also bottom gusset material supply means by which the web of bottom gusset material is supplied. The apparatus must therefore be complicated in structure and high in cost. Furthermore, the apparatus is large sized by the bottom gusset material supply means. A large space is therefore required for installation.
It is therefore an object of the invention to provide a new and improved apparatus which can successively make plastic begs each of which includes a bottom gusset portion incorporated into superposed two layers of panel portion, without involving bottom gusset material supply means.